The present invention relates to a method and a device for controlling an engine.
A quantity controller and a method and a device for checking a sensor for detecting the position of a quantity controller are known from German Published Patent Application No. 40 33 049. With the method described there, a check is performed when the quantity controller is switched to currentless to determine whether a needle motion sensor or a corresponding sensor is delivering an output signal.
In addition, there are conventional methods in which various signals are subjected to a plausibility check with the other signals.
When using an injection quantity signal, the plausibility check with other signals may be problematical due to today""s systems, there are often injections that do not make any contribution to engine torque. These include, for example, pre-injections before the actual injection and post-injections, which are used for exhaust gas treatment or for regeneration of filters and/or catalytic converters.
According to the present invention, on the basis of a first variable which characterizes the injection quantity and a second variable which characterizes the angle setting at which the injection quantity is metered, a third variable which characterizes the torque supplied by the engine may be determined. On the basis of a fourth variable which characterizes the driver""s intent, a fifth variable which characterizes the torque desired by the driver may be determined. The third variable and the fifth variable may be analyzed for the purpose of fault monitoring. This method according to the present invention permits reliable and accurate fault detection, e.g., in the area of fuel metering and/or detection of the driver""s intent. It may be advantageous here that the second variable which characterizes the angular position of the crankshaft or the camshaft during the injection may be taken into account. It may be possible to take into account the influence of the injected fuel on the torque supplied by the engine. The setpoint or the actual value of the start of injection, the start of delivery, the start of actuation or another corresponding variable may be used as the second variable.
It may be advantageous if the actuation duration of an output stage of a solenoid valve or a piezoactuator is used as the first variable. By using actuation signals for the output stage, it may be possible to test the functionality of the entire control unit.
It may be advantageous if the fourth variable corresponds to the position of an operating element. This also makes it possible to detect faults in the area of processing of the output signal of the operating element.
It may be advantageous if a fault is detected when the third variable and the fifth variable differ by more than a threshold value. Through this method, it may be possible to detect faults in the entire signal path of the control system. These include faults in the area of analysis of the input variables, calculation and determination of the output variables.
Due to the fact that the fault monitoring may occur only in certain operating states, this makes it possible to reduce complexity. Furthermore, a more accurate fault detection may be possible because fault detection is not performed in states in which no unambiguous results may be derived.